Multiple-Input Multiple-Output (MIMO) is a technology for improving efficiency of data transmission and reception using multiple transmit antennas and multiple receive antennas rather than using one transmit antenna and one receive antenna. If a single antenna is used, a receive entity receives data through a single antenna path. In contrast, if multiple antennas are used, the receive entity receives data through several paths, accordingly data transmission rate and throughput may be improved, and the coverage may be extended.
To increase multiplexing gain of the MIMO operation, an MIMO transmit entity may use channel state information (CSI) fed back by the MIMO receive entity. The receive entity may determine the CSI by performing channel measurement using a predetermined reference signal (RS) from the transmit entity.
Research has been actively conducted on a coordinated multi-point (CoMP) system for improving throughput for a user at the cell boundary by applying improved MIMO transmission in a multi-cell environment. With the CoMP system, inter-cell interference may be reduced in the multi-cell environment, and overall system performance may be improved. For example, CoMP techniques include joint processing (JP) of performing common computational processing between neighboring cells by grouping multiple neighboring cells and considering the same as a virtual MIMO system and cooperative beamforming (C-BF) capable of solving the problem of inter-cell interference by adjusting a beam pattern between neighboring cells.